Ansar Dine and the Tuareg separatist group MNLA agreed to a ceasefire with the government on December 21.

The truce came a day after the U.N. Security Council approved a West African plan to deploy troops to Mali, with the goal of retaking the north from Ansar Dine and two other Islamist groups.

The two other groups — the Movement for Oneness and Jihad in West Africa and al-Qaida in Islamic Maghreb — have shunned negotiations taking place in Burkina Faso's capital, Ouagadougou.

The Economic Community of West African States is planning to send at least 3,000 troops to Mali to help retrain the army and recapture the north. No military offensive is expected until late this year.

Mali was plunged into chaos after renegade soldiers overthrew the government in March of last year. The MNLA took control of the north with help from the Islamist groups, which then seized power from the separatists.

Rights groups have condemned the militants for a series of abuses, including public executions and amputations, aimed at enforcing the militants' strict form of Islamic law.